Cardiac differentiation is modulated by anti-apoptotic signals in murine embryonic stem cells.

BACKGROUND: Embryonic stem cells (ESCs) serve as a crucial ex vivo model, representing epiblast cells derived from the inner cell mass of blastocyst-stage embryos. ESCs exhibit a unique combination of self-renewal potency, unlimited proliferation, and pluripotency. The latter is evident by the ability of the isolated cells to differentiate spontaneously into multiple cell lineages, representing the three primary embryonic germ layers. Multiple regulatory networks guide ESCs, directing their self-renewal and lineage-specific differentiation. Apoptosis, or programmed cell death, emerges as a key event involved in sculpting and forming various organs and structures ensuring proper embryonic development. However, the molecular mechanisms underlying the dynamic interplay between differentiation and apoptosis remain poorly understood. AIM: To investigate the regulatory impact of apoptosis on the early differentiation of ESCs into cardiac cells, using mouse ESC (mESC) models - mESC-B-cell lymphoma 2 (BCL-2), mESC-PIM-2, and mESC-metallothionein-1 (MET-1) - which overexpress the anti-apoptotic genes Bcl-2, Pim-2, and Met-1, respectively. METHODS: mESC-T2 (wild-type), mESC-BCL-2, mESC-PIM-2, and mESC-MET-1 have been used to assess the effect of potentiated apoptotic signals on cardiac differentiation. The hanging drop method was adopted to generate embryoid bodies (EBs) and induce terminal differentiation of mESCs. The size of the generated EBs was measured in each condition compared to the wild type. At the functional level, the percentage of cardiac differentiation was measured by calculating the number of beating cardiomyocytes in the manipulated mESCs compared to the control. At the molecular level, quantitative reverse transcription-polymerase chain reaction was used to assess the mRNA expression of three cardiac markers: Troponin T, GATA4, and NKX2.5. Additionally, troponin T protein expression was evaluated through immunofluorescence and western blot assays. RESULTS: Our findings showed that the upregulation of Bcl-2, Pim-2, and Met-1 genes led to a reduction in the size of the EBs derived from the manipulated mESCs, in comparison with their wild-type counterpart. Additionally, a decrease in the count of beating cardiomyocytes among differentiated cells was observed. Furthermore, the mRNA expression of three cardiac markers - troponin T, GATA4, and NKX2.5 - was diminished in mESCs overexpressing the three anti-apoptotic genes compared to the control cell line. Moreover, the overexpression of the anti-apoptotic genes resulted in a reduction in troponin T protein expression. CONCLUSION: Our findings revealed that the upregulation of Bcl-2, Pim-2, and Met-1 genes altered cardiac differentiation, providing insight into the intricate interplay between apoptosis and ESC fate determination.

Repressive effect of Rhus coriaria L. fruit extracts on microglial cells-mediated inflammatory and oxidative stress responses.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhus coriaria L. represents a herbal shrub that is used widely in traditional medicine in the Middle East region to treat different diseases including inflammation-related disorders. R. coriaria extracts have been well characterized in terms of their biological activities, pharmacological potential and phytochemical components. However, the effect of R. coriaria on neuro-inflammation has not been studied previously in detail. AIM OF THE STUDY: In the present study, we performed a qualitative phytochemical analysis and investigated the antioxidant and anti-neuro-inflammatory potential of R. coriaria extracts on BV-2 microglial cells. MATERIALS AND METHODS: R. coriaria extracts were prepared using two different solvents: distilled water and ethanol. Phytochemical screening was performed to determine the principal bioactive components. The radical scavenging activity was assessed by DPPH method (2,2-diphenyl-1-picrylhydrazyl). The effect of R. coriaria on neuro-inflammation was studied upon measuring the production of oxidative stress and inflammatory factors using DCF (2',7'-dichlorofluorescein) and Nitric oxide (NO) assays respectively, and by analyzing the mRNA (TNFα, IL-10, iNOS and COX-2) and protein (NFκß) levels of genes involved BV-2 microglia cells-mediated inflammation using quantitative Real Time PCR and Western blot, respectively. RESULTS: We found that R. coriaria extracts contain high phenolic and flavonoid contents. Interestingly, the ethanolic extract exerted a potent anti-inflammatory potential on insulted BV-2 cells manifested by: i) inhibition of Reactive Oxygen species (ROS) production and nitric oxide (NO) release; ii) suppressing TNFα, iNOS and COX-2 mRNA levels; iii) reducing NFκß activation; and iiii) enhancing IL-10 transcription levels. CONCLUSION: Our results indicate that the neuro-inflammation inhibitory activity of R. coriaria extracts involves the inhibition of NF-κB signaling pathway. These findings suggest that R. coriaria might carry therapeutic potential against neurodegenerative diseases.

Murine Embryonic Stem Cell Plasticity Is Regulated through Klf5 and Maintained by Metalloproteinase MMP1 and Hypoxia.

Mouse embryonic stem cells (mESCs) are expanded and maintained pluripotent in vitro in the presence of leukemia inhibitory factor (LIF), an IL6 cytokine family member which displays pleiotropic functions, depending on both cell maturity and cell type. LIF withdrawal leads to heterogeneous differentiation of mESCs with a proportion of the differentiated cells apoptosising. During LIF withdrawal, cells sequentially enter a reversible and irreversible phase of differentiation during which LIF addition induces different effects. However the regulators and effectors of LIF-mediated reprogramming are poorly understood. By employing a LIF-dependent 'plasticity' test, that we set up, we show that Klf5, but not JunB is a key LIF effector. Furthermore PI3K signaling, required for the maintenance of mESC pluripotency, has no effect on mESC plasticity while displaying a major role in committed cells by stimulating expression of the mesodermal marker Brachyury at the expense of endoderm and neuroectoderm lineage markers. We also show that the MMP1 metalloproteinase, which can replace LIF for maintenance of pluripotency, mimics LIF in the plasticity window, but less efficiently. Finally, we demonstrate that mESCs maintain plasticity and pluripotency potentials in vitro under hypoxic/physioxic growth conditions at 3% O2 despite lower levels of Pluri and Master gene expression in comparison to 20% O2.

The Oct4 protein: more than a magic stemness marker.

The Oct4 protein, encoded by the Pou5f1 gene was the very first master gene, discovered 25 years ago, to be absolutely required for the stemness properties of murine and primate embryonic stem cells. This transcription factor, which has also been shown to be essential for somatic cell reprogrammation, displays various functions depending upon its level of expression and has been quoted as a "rheostat" gene. Oct4 protein is in complexes with many different partners and its activity depends upon fine post-translational modifications. This review aims at revisiting some properties of this protein, which has not yet delivered all its potentialities.

Oct-3/4 dose dependently regulates specification of embryonic stem cells toward a cardiac lineage and early heart development.

The transcriptional mechanisms underlying lineage specification and differentiation of embryonic stem (ES) cells remain elusive. Oct-3/4 (POU5f1) is one of the earliest transcription factors expressed in the embryo. Both the pluripotency and the fate of ES cells depend upon a tight control of Oct-3/4 expression. We report that transgene- or TGFbeta-induced increase in Oct-3/4 mRNA and protein levels in undifferentiated ES cells and at early stages of differentiation triggers expression of mesodermal and cardiac specific genes through Smad2/4. cDNA antisense- and siRNA-mediated inhibition of upregulation of Oct-3/4 in ES cells prevent their specification toward the mesoderm and their differentiation into cardiomyocytes. Similarly, Oct-3/4 siRNA injected in the inner cell mass of blastocysts impairs cardiogenesis in early embryos. Thus, quantitative Oct-3/4 expression is regulated by a morphogen, pointing to a pivotal and physiological function of the POU factor in mesodermal and cardiac commitments of ES cells and of the epiblast.

Cardiac commitment of embryonic stem cells for myocardial repair.

Embryonic stem (ES) cells represent a source for cell-based regenerative therapies of heart failure. The pluripotency and the plasticity of ES cells allow them to be committed to a cardiac lineage following treatment with growth factors of the transforming growth factor (TGF)-beta superfamily. We describe a protocol designed to turn on expression of cardiac-specific genes in undifferentiated murine ES cells stimulated with BMP2 and/or TGF-beta. Cell commitment results in a significant improvement in spontaneous cardiac differentiation of ES cells both in vitro and in vivo.

Cardiac specification of embryonic stem cells.

Over the past decade, cell transplantation has been recognized as a mean of repairing infarcted myocardium. Both adult stem cells and differentiated cells have yielded encouraging results with regard to engraftment into postinfarction scars. However, these cells now feature serious restrictions. Asan alternative, embryonic stem (ES) cells are particularly attractive, because of their plasticity and the subsequent possibility to drive them towards a cardiomyogenic phenotype after exposure to appropriate growth factors. An additional theoretical advantage of ES cells is their expected immune privilege. In this article, we summarize the findings obtained in cell therapy using ES cells and discuss the molecular mechanisms of cardiac specification of the cells.